ON PAPER this looked a suspect proposition: after all, who goes to see Eric Clapton’s band sans Eric? But Captain Beefheart’s Magic Band were always more than sidemen; these were players inducted into the secrets of the Captain’s musical universe during long rehearsals in which creative tensions could mean swinging fists. No musician sounded quite the same again.

This five-piece line-up has briefly reconvened after encouragement from a longtime fan of the music, Matt Groening, creator of The Simpsons. And, with the Captain having changed careers 20 years ago to paint and sculpt in the Mojave Desert, this packed London show is a rare chance to revisit the sublime mysteries of Floppy Boot Stomp and I’m Gonna Booglarize You Baby.

A muscular, defiantly odd bass solo from Rockette Morton sets the tone before the group lurches into a string of old Beefheart instrumentals, or hits rearranged as instrumentals. Hair Pie: Bake 1, Alice in Blunderland and Abba Zaba whizz by. The band emits a vast, unlikely racket: imagine ZZ Top playing free jazz. The drummer, John “Drumbo” French, juggles polyrhythms; Morton’s bass is a stop-start rumble as spindly lead lines and fractured chords are traded between guitarists Gary Lucas and Denny Whalley. It’s a reminder that no other band has done more to battle the tyranny of rock’s four-four beat.

Morton is paunchy, Santa Claus-bearded, grinning madly; Whalley, in an Iron Cross T-shirt, resembles an aged Noddy Holder. But Lucas retains some rock star cool in ponytail and leather jacket.

His solo, Evening Bell, from the Ice Cream for Crow album, is a web of spiderish invention. But elsewhere much of the detail of these intricate free jazz/rock/blues constructions is lost in the murk of the Empire’s soupy acoustics.

Just as it looks as if instrumentals aren’t going to be enough to sustain a show, Drumbo announces he will sing (another Beefheart alumnus, Robert Williams, takes over on drums). Incendiary performances of Click Clack and Sun Zoom Spark then demonstrate that beyond the weirdness of Trout Mask Replica, Beefheart’s true metier was as a great white bluesman.

They end with Big Eyed Beans from Venus; thousands of middle-aged gents go wild. He may say he has renounced music, but someone should send the Captain a tape.